electrical connector



J. F. NISULA 3,124,409

ELECTRICAL CONNECTOR Filed Dec. 11, 1961 March 10, 1964 INVENTOR.

I JaZgyfl/Vldw/w United States Patent 3,124,409 ELECTRICAL CONNECTOR John F. Nisula, Cedar Rapids, Iowa, assignor to Square D Company, Park Ridge, 111., a corporation of Michigan Filed Dec. 11, 1961, Ser. No. 158,365 8 Claims. (Cl. 339-272) This invention relates generally to electrical connectors, and more; particularly to an electrical connector particularly adapted to connect an electrically conductive wire composed mainly of aluminum to an electrically conductive terminal strap composed mainly of copper and forming part of an electrical device such as a switch or circuit breaker.

The different coefiicient of thermal expansion between copper and aluminum and the tendency of non-conductive oxides to form rapidly on aluminum surfaces make it difficult to maintain a good electrical connection between a copper conductor and an aluminum conductor.

An object of the invention is to provide an improved connector for electrically joining copper and aluminum conductors wherein the copper conductor is resilient and is so shaped that its resiliency aids in maintaining a tight connection with low resistance. Other objects will appear when the following specification is considered in conjunction with the accompanying drawings wherein:

FIGURE 1 is a perspective view of a connector constructed in accordance with the invention and including a broken off portion of a copper conductor forming a part of an electrical device;

FIGURE 2 is a sectional view of the connector of FIG- URE 1 taken generally along the line 2-2 of FIGURE 3;

FIGURE 3 is a sectional view taken generally along the line 33 of FIGURE 2;

FIGURE 4 is a sectional view taken generally along the line 4-4 of FIGURE 2; and

FIGURE 5 is a perspective view of an aluminum clamping shoe forming a part of the connector.

In the drawings, the connector includes a body 12 formed of an aluminum alloy and having an aperture 13 of rectangular cross section extending therethrough. An end portion 14 of an electrical conductor formed of a copper alloy and which may constitute a part of an electrical device (not shown) extends into the aperture 13 for engagement with an inner surface of a lower portion 17 of the body 12, and a clamping shoe 16 formed of an aluminum alloy is positioned in the aperture 13 for engagernent with the conductor end portion 14 on the opposite side thereof from the lower portion 17 of the body 12. An upper portion of the body 12 is provided with a threaded aperture for receiving a clamping screw 20 preferably formed of steel and adapted to clamp an end of an electrically conductive wire 18 receivable in the aperture 13 against the clamping shoe 16.

An electrical connection of low resistance between the wire 18 and the end portion 14 of the copper alloy conductor is able to be maintained by a connector 10 constructed in accordance with the invention when the wire 18 is formed of an aluminum alloy, and also when the wire 18 is formed of a copper or other metal alloy.

The lower portion 17 of the body 12 is formed with a "downwardly projecting portion or rib 21 adapted to be held by the end portion 14 in a recess (not shown) in the casing of an electrical device to secure the body 12 thereto. The clamping screw 20 is provided with a slot 22 for receiving the tip of a screw driver (not shown).

The provision of the aluminum alloy clamping shoe 16 between the wire 18 and the end portion 14 of the copper alloygconductor of the electrical device has been found to resultin a better electrical connection than when a wire 18 of aluminum is clamped directly to the end portion 14. The clamping shoe 16 is formed with a concave upper surice face 24 to provide a larger area of contact with the wire 18 than if the surface 24 were flat. A bottom surface 25 of the clamping shoe 16 is generally flat, but has a pair of recesses 26 and 27 therein generally triangular in cross section and formed by forming tools in a well known manufacturing operation which also forms a pair of ribs 28 and 29 on the upper surface 24 which are spaced longitudinally of and extend transversely to the wire 18 for better gripping thereof. A pair of ears 30 and 31 are formed on one end of the clamping shoe 16 to prevent the clamping shoe from sliding out of the body portion 12 in the direction of the other end.

In accordance with the invention, the copper alloy conductor'end portion 14 is preferably formed of a high tensile strength bronze having a Rockwell B hardness of 72 to 84, in order that it may have a degree of resiliency. As best shown in FIGURE 3, the end portion 14 may be formed centrally thereof with a concavo-convex portion to'provide a downwardly concave lower surface 34 and an upwardly convex upper surface 35 thereon. Other shapes could also be given to the end portion 14 to render it resiliently deformable. In the clamping of the wire 18, the screw 22 is tightened sufficiently to cause the clamping shoe 16 to resiliently deform the end portion 14 in a manner which tends to flatten the curved cross section. Then, if any looseness develops as a result of alternate thermal expansion and contraction of the parts in cycles of use, the end portion 14 tends to resume its original curved shape, thus compensating for any slack and maintaining a good electrical connection.

Various modifications may be made in the structure disclosed without departing from the spirit and scope of the invention.

I claim:

1. An electrical connector comprising:

(a) a body formed of an aluminum alloy and having an aperture extending therethrough,

(b) an electrical conductor formed of a resilient copper alloy and having an end portion extending into said aperture in engagement with a lower portion of said body,

(0) a clamping shoe formed of an aluminum alloy and positioned in said aperture in engagement with said end portion of said electrical conductor on the opposite side thereof from said lower portion of said body, said end portion of said electrical conductor being shaped differently from the engaging surfaces of said clamping shoe and said lower portion of said body so as to be resiliently deformable thereby, and

(d) clamping means associated with an upper portion of said body and adapted to clamp an end of an electrically conductive wire against said clamping shoe and to resiliently deform said end portion of said electrical conductor by compression thereof between said clamping shoe and said lower portion of said body.

2. An electrical connector as claimed in claim 1, wheresaid end portion of said copper alloy electrical conductor is provided with a portion having a concaveconvex cross section.

3. An electrical connector as claimed in claim 1,

wherein said clamping shoe is provided with a generally flat bottom surface for engaging said end portion.

4. An electrical connector as claimed in claim 1,

wherein said lower portion of said body is provided with a generaly flat surface partially defining said aperture.

5. An electrical connector as claimed in claim 1,

wherein said clamping shoe is provided with an upwardly-concave curved surface for engagement with said end of said electrically conductive wire. 6. An electrical connector as claimed in claim 1, wherein an upper surface of said clamping shoe is provided with an upstanding rib for gripping said end of said electrically conductive wire. 7. An electrical connector as claimed in claim 1, wherein an end of said clamping shoe protrudes from one side of said body and is provided with an ear preventing displacement of said clamping shoe toward the other side of said body. 8. An electrical connector as claimed in claim 1, wherein said clamping means includes a screw threadedly received by said upper portion of said body and adapted to extend into said aperture.

References Cited in the file of this patent UNITED STATES PATENTS Reeve Dec. 19, 1905 Rogofi Nov. 11, 1941 Kingdon Jan. 30, 1951 Heath Dec. 6, 1955 FOREIGN PATENTS France Sept. 7, 1942 France Sept. 27, 1943 France Apr. 15, 1953 Germany Dec. 19, 1938 Switzerland Feb. 17, 1936 Switzerland Sept. 16, 1944 

1. AN ELECTRICAL CONNECTOR COMPRISING: (A) A BODY FORMED OF AN ALUMINUM ALLOY AND HAVING AN APERTURE EXTENDING THERETHROUGH, (B) AN ELECTRICAL CONDUCTOR FORMED OF A RESILIENT COPPER ALLOY AND HAVING AN END PORTION EXTENDING INTO SAID APERTURE IN ENGAGEMENT WITH A LOWER PORTION OF SAID BODY, (C) A CLAMPING SHOE FORMED OF AN ALUMINUM ALLOY AND POSITIONED IN SAID APERTURE IN ENGAGEMENT WITH SAID END PORTION OF SAID ELECTRICAL CONDUCTOR ON THE OPPOSITE SIDE THEREOF FROM SAID LOWER PORTION OF SAID BODY, SAID END PORTION OF SAID ELECTRICAL CONDUCTOR BEING SHAPED DIFFERENTLY FROM THE ENGAGING SURFACES OF SAID CLAMPING SHOE AND SAID LOWER PORTION OF SAID BODY SO AS TO BE RESILIENTLY DEFORMABLE THEREBY, AND (D) CLAMPING MEANS ASSOCIATED WITH AN UPPER PORTION OF SAID BODY AND ADAPTED TO CLAMP AN END OF AN ELECTRICALLY CONDUCTIVE WIRE AGAINST SAID CLAMPING SHOE AND TO RESILIENTLY DEFORM SAID END PORTION OF SAID ELECTRICAL CONDUCTOR BY COMPRESSION THEREOF BETWEEN SAID CLAMPING SHOE AND SAID LOWER PORTION OF SAID BODY. 